Hibernate：在OneToMany关系中选择where in

Question

以下是我（缩写）的实体：

@Entity
public class User {

    @OneToMany(fetch=FetchType.LAZY)
    @JoinTable(name="user_items",joinColumns=@JoinColumn(name="user_id"),inverseJoinColumns=@JoinColumn(name="useritem_id"))
    private Set<UserItem> items = Sets.newHashSet();

}


@Entity
@Inheritance(strategy=InheritanceType.JOINED)
public class UserItem {

    @Id
    @Type(type=EntityConstants.TYPE_UUID)
    @Column(columnDefinition=EntityConstants.COL_UUID)
    private UUID id;

}

@Entity
public class UserItemFurniture extends UserItem {

}

现在我想通过其UUID获取UserItemFurniture，但仅当存在User的items时。以下是我的尝试：

em
    .createQuery(
        "SELECT f " +
        "FROM UserItemFurniture f " +
        "WHERE f.id = :iid " +
        "AND f IN (SELECT u.items FROM User u WHERE u.id = :uid) ",
        UserItemFurniture.class
    )
    .setParameter("uid", userId)
    .setParameter("iid", itemId)
    .getSingleResult();

但是它生成了这个毫无意义的SQL语句：

select useritemfu0_.id as id17_, useritemfu0_1_.item as item17_, useritemfu0_.roomNumber as roomNumber18_, useritemfu0_.x as x18_, useritemfu0_.y as y18_
from UserItemFurniture useritemfu0_ inner join UserItem useritemfu0_1_ on useritemfu0_.id=useritemfu0_1_.id
where useritemfu0_.id=? and (useritemfu0_.id in (
    select .
    from _User user1_, user_items items2_, UserItem useritem3_
    where user1_.id=items2_.user_id and items2_.useritem_id=useritem3_.id and user1_.id=?
))
limit ?

请注意子查询：SELECT .

我能否在不使用本地或多个查询的情况下完成此操作？请注意，UserItem没有对User的引用，这是有意为之。

- Bart van Heukelom

---

你尝试过使用“id”限制“IN”子句吗？类似这样：...AND f.id IN (SELECT u.items.id FROM User ... - Xavi López

无法使用u.items.id，因为作为集合值路径的items指整个集合，因此它没有属性id（即使集合的元素有）。 - Mikko Maunu

Answer 1

以下查询可用：

SELECT f
FROM UserItemFurniture f
WHERE f.id = :uid AND EXISTS 
  (SELECT u FROM User u
   WHERE u.id = :iid and f MEMBER OF u.items)

- Mikko Maunu